Mechanical face seals, sometimes referred to as face seals, metal face seals, metal-metal face seals, or similar terms, are used in many types of industrial equipment including mining trucks and track-type machines designed for hauling, excavating, and/or material moving, for example. Mechanical face seals are designed to protect machine components, such as bearings and drive train parts, for example, by keeping out dirt, mud, debris, etc., and by preventing leakage of protective lubricants such as grease and oil. Machines that employ mechanical face seals typically operate in environments that may be highly destructive to the seals themselves, as well as to the components they are designed to protect should the seals begin to leak or otherwise fail. As a result, they must be able to withstand heavy loads, high velocities, increased temperatures, and harmful effects of dirt and debris.
The use of mechanical face seals has greatly improved and extended the life of the various components they are designed to protect. However, these seals are still subjected to conditions that are destructive to the seals, and failure of such seals may occur rapidly and without warning. Such seals generally include a pair of interacting seal rings, one of which may rotate and the other of which may be stationary. Seal size, e.g., diameter of a seal ring, may vary depending on the size of the associated components protected by the seal and/or the size of the machine involved. Destructive temperatures may be reached adjacent the location where one sealing surface contacts another in view of the pressure between the pair of seal rings, and the relative movement of the sealing surfaces. For mechanical face seals that are large in diameter, for example in large machines where face seals may be on the order of three or more feet in diameter (typical face seal diameters may range between about 87 mm and about 780 mm), the surface velocity at the seal face may be substantial relative to much smaller seals since, for a rotating body, speed increases as diameter increases. This increase in velocity may result in increased heat and destructive forces. Under some conditions, dirt and debris can enter between the seal faces. This dirt and debris may increase the coefficient of friction between seal faces with resulting increase in temperature and seal ring heat damage. It would be beneficial to have an effective way to mitigate heat damage to face seals and make seal rings more durable.
The seal rings of mechanical face seals typically are manufactured by casting in view of the solid geometry of the seal rings. The casting process for seal rings employs specific alloy materials which may be costly. It also tends to yield seal rings that are heavier than they need to be, and more costly than they should be due to the increased alloy material. Solidly cast seal rings also have reduced thermal conductivity. As a result, heat generated at the interface where a pair of seal rings contact may be difficult to dissipate. Solid seal rings formed by casting have been successfully employed in heavy equipment for many years. However, it would be beneficial and desirable to develop a way to form seal rings with geometries that are optimized to be sufficiently robust so as to endure the forces to which they may be subjected, to use less expensive alloy or other material than in a casting process, to be lighter in weight, and to be capable of reducing heat build-up at the interface where a pair of seal rings contact.
A way to monitor friction in a mechanical seal with surfaces that move relative to one another is described in U.S. Patent Application Publication 2012/0112416 of Berger et al. that was published on May 10, 2012 (“the '416 publication”). Specifically, the '416 publication discloses stationary and rotating seal rings with interacting sealing surfaces, and a monitoring device associated with the stationary seal ring that employs a strain gauge to detect variations in friction at the sealing interface. The '416 publication discloses determining the friction torque at the stationary seal ring, and discloses that this enables a secure judgment of a “tribological” state at the sliding surfaces. In turn, this enables early intervention in taking measures against increased wear at the sliding surfaces between seal rings.
Although the monitoring device of the '416 publication may offer a way to detect variations in friction at the sealing face of the seal rings, it may be only partially effective and does not provide structures on the seal rings to counter heat build-up at the sealing face. The strain gauge employed in the '416 publication indirectly measures friction by sensing torque transmitted to the stationary seal ring. However, the monitoring device does not provide a way to mitigate temperature build-up and dissipate heat that occurs at the sealing face which could be detrimental to the seal. In addition, the '416 publication does not address the forming process for the seal rings or how the seal rings may be formed more economically and of lighter weight.
The mechanical face seal of the present disclosure addresses one or more of the needs set forth above and/or other problems of the prior art.